Fix A2A title and OpenAI example to use ChatPrompt

Co-authored-by: heyitsaamir <[email protected]>

Author: Copilot

packages/a2aprotocol/README.md

@@ -1,4 +1,4 @@
-# Microsoft Teams A2A Protocol
+# Microsoft Teams A2A
 
 <p>
     <a href="https://pypi.org/project/microsoft-teams-a2a/" target="_blank">

packages/openai/README.md

@@ -26,8 +26,8 @@ uv add microsoft-teams-openai
 
 ```python
 from microsoft.teams.openai import OpenAICompletionsAIModel
-from microsoft.teams.ai import Agent
+from microsoft.teams.ai import ChatPrompt
 
 model = OpenAICompletionsAIModel(api_key="your-api-key", model="gpt-4")
-agent = Agent(model=model)
+prompt = ChatPrompt(model)
 ```